Global warming caused by the increase of the concentration of greenhouse gasses, especially carbon dioxide, in air is becoming ever more evident and is changing the global ecosystem. In 2007, the United Nations Intergovernmental Panel on Climate Change (IPCC) published its Fourth Assessment Report, projecting that if global warming is not effectively controlled, human being will face severe consequences. Another report, Meeting the Climate Change, published in 2005 by the International Climate Change Task Force, clearly pointed out that the continuous rising of global temperature within the next decades would cause extreme weather events, such as more destructive and frequent droughts and floods, sea level rising which damages communities, cities and island nations, and agricultural production.
One of the consequences of global warming is desertization, the process or evolution of land mass becoming dry, arid and barren. Desertization has been a major problem on a global scale, and is largely caused by the continued environment hazards brought about by human activities, and especially the green house effect. A study by Compton J. Tucher et al. revealed that the Sahara desert in Africa unsteadily expanded southward for about 130 kilometers from 1980 to 1990. In China, where desert land is estimated to make up about 17% of its total land, desert area is increasing at an annual rate of 2,460 square kilometers. In those provinces where desert boundaries are located, annual desertization rate is more than 4%, severally impacting local human and natural habitats.
There have been many efforts worldwide to try to reduce the threat of global warming. One of the leading solutions is to cut carbon dioxide emission in order to reduce the greenhouse effect. The Kyoto Protocol as established by the United Nations Framework Convention on Climate Change and ratified by its member countries requires, in the form of a treaty, the countries' commitments to reduce their emissions of carbon dioxide and five other greenhouse gases, or engage in emissions trading if they maintain or increase emissions of these gases. However, this solution is at the cost of economical development, and countries such as United States and Australia have chosen to stay away from it.
Another more attractive way is to remove carbon dioxide from the atmosphere in order to reduce carbon dioxide concentration. Professor Klaus Lackner at Columbia University has successfully developed a carbon dioxide in air capture technology, and designed a synthetic tree to absorb carbon dioxide from the atmosphere. He proposed that eventually the removed carbon dioxide would be stored underground safely and permanently. However, running the synthetic tree requires a lot of energy, inevitably generating more carbon dioxide. In 1986, Dr. John Martin of the Moss Landing Marine Laboratory proposed to pour iron fertilizer in Antarctic Ocean to create algae bloom based on the hypothesis that algae did not grow well in ocean due to iron deficiency. Millions of square miles of algae gardens can be created to consume billions of tons of carbon dioxide. Many small scale experiments have been conducted to prove that Dr. Martin's proposal can become a working solution to global warming. However, scientific evidence is so far incomplete. And the scale of iron enrichment and algae growth may cause unintended consequences, such as interruption of the ocean ecosystem.
Other proposals have been put forth in order to prevent global warning. In 2006, Roger Angel, a noted astronomer at the University of Arizona, outlined a plan to put into orbit trillions of small lenses that would bend sunlight away from earth. However, it will take tens of millions of rocket launches and cost a tremendous amount of resources to implement the plan. Further, it will reduce sunlight on earth, which will slowdown vegetation growth and consequently result in less carbon dioxide consumption from air.
Some took lessons from the nature's offering. In 1991, the volcano eruption on Mount Pinatubo of Philippines discharged millions of tons of sulfur dioxide into atmosphere, resulting in a worldwide temperature decrease over the next few years. Inspired by the event, some scientists, including Nobel laureate Paul Crutzen, proposed to inject huge amount of sulfur dioxide into atmosphere to form a sunlight deflecting layer in order to reduce sunshine intensity on earth and atmospheric temperature. However, it is believed that such proposal is too risky to implement for the time being and may cause environmental consequences such as degraded water supply quality and acid rain.
The Mother Nature has actually provided the most original and effective solution to the greenhouse effect and global warming—photosynthesis—that takes sunlight and absorbs carbon dioxide from air and produces glucose and emits oxygen. Many considered utilizing the vast desert area to grow plants, which not only removes carbon dioxide but also helps absorb other pollutants from air. One proposal was to air drop drought-resistant plant seeds during rain season, in hope that plants will grow up to alter the dry and arid condition. However, due to the hostile environment in desert, such as the extreme temperature fluctuation between day and night and the lack of water and nutrients, the efforts yielded little success. Human-aided forestation in desert area has also been attempted in many places. Nevertheless, due to the lack of requisite water and nutrients planted trees could not grow strong enough to counter the severe sun exposure and the destructive force of sandstorms. Efforts in this regard were proven to be ineffective.
Chinese Patent Application No. 00122918.4 by Yuanyong Sheng discloses a practice of planting square matrix of dummy trees to form an X-shaped and interconnected base to block wind and sandstorm at ground level. However, dummy trees themselves take land space and do not consume carbon dioxide. Also, they are incapable of protecting plants from severe sunlight damage. Another Chinese Patent Application, No. 200410081493.2 by Yu Cao, provides a closed transparent structure with water-collecting and irrigation systems. The closed transparent structure keeps water from evaporating. However, plants raised in this type of environment have great difficulties to survive in open desert. So the closed structure needs to stay with the plants. And, the invention is suitable to small areas, but not to be expanded to cover large areas.